1. Technical Field
This invention generally relates to power supplies, and more specifically relates to programmable power supplies for driving multiple loads.
2. Background Art
Power supplies come in a variety of different shapes, sizes, and functional capabilities. One type of power supply that is well-known is the programmable power supply that provides multiple output channels that may be programmed to drive multiple loads. For example, bench power supplies for use by technicians often have the capability of setting a particular output to a wide range of voltage and current capability, and may allow for both direct current (DC) and alternating current (AC) outputs. These highly programmable bench power supplies are very expensive, some costing thousands of dollars. On the other end of the spectrum are small, dedicated power supplies that are manufactured to power a known load at a specified voltage and current. These types of power supplies are typically very inexpensive, but are suitable only for their specific, designed use.
Sign controllers are also known in the art that provide power to different circuits in a defined sequence to provide an animated sign. For example, a sign with an arrow made of light bulbs may divide the arrow into four different circuits, then use a sign controller that sequences the four circuits in a manner that makes the arrow appear to grow larger until the entire arrow is lit. Sequenced controllers are well-known in the art for controlling signs. Known sequenced controllers include motors with mechanical contactors, and solid-state controllers that use relays or triacs to drive the loads under control of a state machine or microprocessor.
A relatively recent development in the sign industry is to make a sign from an electroluminescent (EL) panel that has multiple segments that may be individually driven. In addition, recent developments have used printed polymer inks, or other phosphorescent materials, such as organic light-emitting diodes (OLEDs). With any of these technologies that allow defining multiple segments, the different segments typically are overlaid with artwork. By individually driving the segments under control of a state machine or microprocessor, the sign may be animated. There are two significant problems with the prior art methods of powering a multiple-segment EL panel sign. The first problem relates to the electrical connections to the sign itself. The current state of the art uses pigtail wire connections on the back of the sign that are connected to a connector. These pigtail wire connections are a point of common failure. The second problem relates to the design of the power supply for a particular sign. Currently, power supplies for powering an EL panel sign are custom-designed for the particular sign. Thus, if a sign with six segments needs to be powered, a power supply with six output channels is provided with the desired sequence of animating the sign being hard-coded into the power supply. The problem with this approach is that EL panels degrade over time, and eventually wear out. When the EL panel wears out, the EL panel and the power supply are typically thrown away. Because the power supply is unique to the particular sign, the power supply is not reusable for different types of signs. Without a way to provide a programmable power supply that may be reused with a variety of different signs, the sign industry will continue to suffer excessive costs by discarding power supplies that are specifically designed to work only for a particular sign.